Effect of organic compounds on nanoparticle formation in diluted diesel exhaust U. Mathis1, M. Mohr1, and R. Zenobi2 1EMPA, Swiss Federal Laboratories for Materials Testing and Research, Laboratory for Internal Combustion Engines, CH-8600 Dübendorf, Switzerland 2ETH Hönggerberg, Swiss Federal Institute of Technology, Chemistry Department, CH-8093 Zürich, Switzerland
Abstract. The nucleation of nanoparticles in the exhaust of a modern light-duty diesel
vehicle was investigated on a chassis dynamometer. This laboratory study is
focused on the influence of volatile organic compounds (VOCs) on nucleation
of volatile nanoparticles. Different organic compounds were added to the dilution air of the particle sampling under different sampling conditions.
Sample temperature and relative sample humidity were varied in a wide range.
The number size distribution of the particles was measured with a scanning
mobility particle sizer (SMPS) and showed significant differences in response to the added organic compounds. While the nucleation mode particles
showed a large variation in concentration, the accumulation mode particles
remained unchanged for all compounds. Depending on the functional group, organic compounds were capable of initiating and increasing (alcohols and
toluene) or decreasing (acetone, aniline, and methyl tert-butyl ether (MTBE)) nucleation mode particles. Short volatile aliphatic hydrocarbons
(hexane and cyclohexane) turned out to be without effect on nucleation of
nanoparticles. Possible reasons for the differences are discussed.
Citation: Mathis, U., Mohr, M., and Zenobi, R.: Effect of organic compounds on nanoparticle formation in diluted diesel exhaust, Atmos. Chem. Phys., 4, 609-620, doi:10.5194/acp-4-609-2004, 2004.